Fix allocation of temporary buffer in `Wcsprm.set`.  The number of axes
returned may be up to twice as many as requested.  Rather than being
smart about it, just allocate the buffer to be twice as large -- these
are very small buffers in any case (one int per dimension).
Merge pull request #2350 from mdboom/wcs/invalid-read

Fix allocation of temporary buffer in `Wcsprm.set`.